Heating furnace



Sept. 12, 1933. C A. L. cULBERTsYoN HEATING FURNACE `Filed April 18, 1930 s sheets-sheet 1 Sept. 12, v1933.*.7 A.,|.. cuLBERTsoN 1,926,714

HEATING FURNACE Filed April 18, 1930 5 Sheets-Sheet 2 [mein-07:

@MFM/f Sept. 12, 1933. A.A L. 'cLB'E-rs'oN HEATING FURNACE `s sheets-smet a Filed April 18, 1930 www Mm.

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Patented Sept. 12, 1933 UNITED STATES lPATENT OFFICE HEATING FURNAGE l Albert L. Culbertson,

deceased Application April 18, 1930. Serial No. 445,243

6 Claims.

This invention relates to furnaces and methods of operating the same and, while not limited thereto, relates more particularly to furnaces known as soaking pits used for reheating ingots to the temperature necessary for forging or rolling; and equipped with air preheating apparatus.

Heretofore in operating furnaces or pits of this class it has been customary to direct a very hot flame into the furnace to heat the ingots in as' short a time as possible. This hot flame will raise the parts of the ingots with which it first contacts to a very high temperature while the remainder stays comparatively cool. Therefore it is necessary for the operators to watch the heating operation and shut off or regulate the fuel and thereby the flame when the hottest parts of the ingots reach a predetermined temperature in order to prevent burning or overheating. The ingots are then permitted `to soak, that is, the heat from the hottest portions of the ingots is permitted to travel through the ingots to the cooler portions. After the ingots have 'soaked sufficiently, the fuel is again turned on and ame reestablished to again heat the ingots until they again approach the molten state at the point of contact with the flame. The fuel is again shut off or regulated and the ingots again permitted to soak. This alternate heating and soaking is continued until the ingots are heated to an even temperature throughout. The regulation of the flame depends upon the judgment of the operators and since said judgment is often faulty, excessive scaling and burning of the ingots results.

At best under this old method of heating the time required is excessive dueto the periods of soaking which are necessary.

The present method has foi` its object the provision of a novel method whereby the heating of the ingots may be carried on continuously without burning the ingots and the time necessary for heating will be materially reduced.

In over-fired pits, such as shown in the accom- 45 panying drawings, the firing port is at the upper end of the pit, and the outlet port for the products of 4combustion is at the lowerend of the port so that in order to force the flame down to the lower part of the pit, the flame pressure must be maintained; therefore reduction of the gas and air supply to reduce the temperature of the flame is not practical with this class of pit furnace.

The present invention provides apparatus and 55 method whereby the flame temperature may be reduced without reducing the ame volume and pressure so that when the upper ends of the ingots or other materials being heated are raised to a predetermined temperature, the flame temperature may be reduced to a point approximating or below the temperature of the upper ends of the ingots. Thus the temperature of the upper ends of the ingots will not be further heated but the reduced temperature name-will continue to heat the lower portions of the ingots which are below the desired temperature.

The present method consists in providing for the flow of products of combustion into the mixing chambers of the fuel burners of the respective pits to lean down the fuel mixture when it is desired to reduce the flame temperature,

In the drawings:

Figure l is a plan view of a furnace layout constructed in accordance with this invention.

Figure 2 is a side elevation of the furnace, partly in section and partly broken away.

Figure 3 is a sectional plan view of the preheater of the furnace.

Figure 4 is a vertical transverse section through the preheater.

Referring more particularly to the drawings, the numeral 2 designates the several pits of the furnace, each of which is separate from the other and each of which is provided with a door or closure member 3 at its top. Each of the pits has its rear wall, adjacent its top, provided with a 8 pair of burner ports 4 which open at their rear ends into a. mixing chamber 5. A gas supply manifold conduit 6 extends along the several pits 2 and is provided with branches 6a which communicate with the mixing chambers 5. through the bottom walls thereof. Eachof the branches 6a is provided with a manually operated shut-off valve 7.

An air manifold conduit 8 extends along the several pits 2 and is provided with branch conduits 8a which lead to each of the mixing chambers 5. A pair of nozzles 9 lead from each air branch conduit 8a into the mixing chambers 5 through the back walls thereof on a line with the burner ports 4. A manually operated shut-01T valve 9a is provided in each of the branch conduits 8a.

'Ihe pits 2 are provided with prts 10 in their rearwalls adjacent the bottoms thereof through which the products of combustion pass from the pits. The ports 10 communicate with branch conduits or nues 12 which in turn are connected to a waste gas manifold conduit 13. A manually operated shut-01T valve or damper 14 is mountedin each of the branch conduits l2. no

The gas manifold 6 is connected to a gas supply main 15 leading from any suitable source of gas supply, such as a gas producer or a source of natural gas.

The air manifold 8 is connected by a main hot air supply conduit 16 leading from the hot air outlet of a continuous air -regenerator 17.

The waste gas manifold 13 is connected by a main waste gas conduit or iiuel which leads to a main waste gas stack 19.

The regenerator 17 per se is a standard apparatus and comprises a heat insulated, substantially rectangular chamber or body 20 mounted on a brick or other heat .insulating base 21. The chamber or body is divided into three sub-chambers 22 by transverse walls 23 composed of brick or other heat insulating material. Each subchamber is provided with a plurality of metal heater plates 24 which are suspended therein and are adapted to be heated to a high temperature by the hot waste gases and to give off said heat to the air passed through said sub-chamber.

A hot waste gas conduit or flue 25 is formed in the base 21 and communicates with each of the sub-chambers 22 through ports 26. A cooled waste gas .conduit or ue 27 extendsV along the top of the chamber 20 and communicates with each of the sub-chambers 22 through ports 28.

A cold air conduit or flue 29 extends along the top of the chamber 20 and communicates with each of the sub-chambers 22 through ports 30. A hot or heated air flue 31 is formed in the base 21 and communicates with each of the sub-chambers 22 through ports'32.

The ports 26 and 28 of each chamber are controlled by valve-disks 26a and 28, respectively, mounted on a single, vertically movable valve-rod 33, while the ports 30 and 32 of each chamber are controlled by valve-disks 30"L and 32B, respectively, mounted on a single, vertically movable valve-rod 34. The valve-rods 33 and 34 of each chamber lare connected to a valve-rocker 35 adapted to alternately raise and lower the rods 33 and 34 so as to open and close the valves carried thereby. By thus operating the valves 26, 28, 30a and 32, hot gases are rst allowed to pass into the sub-chamber 22 through the ports 26 and out through the ports 2 8, thus heating the heater plates 24, then cold air is permitted to ow into the sub-chambers 22 through the ports 30 and become heated by contact with the heater plates 24 and then pass out through the ports 32.

The valve-rockers 35 of the three sub-chambers are adapted to be operated by cam members 36 mounted on a shaft-31 journaled on the top of the regenerator 17 and connected by gearing 38 to a motor 39.

The cams 36 are so adjusted that the valves controlling the flow of air and waste gases will be opened and closed so that one sub-chamber is on air while one is on gas or being heated, while a third sub-chamber is closed, it having been previously heated. This previously heated sub-chamber is then opened to air as the one previously on air is reversed and put on gas. The openingl of the previously heated sub-chamber is arranged so as to overlap the closing of the sub-chamber previously on air so as to not interrupt the flow of heated air. The sub-chambers are reversed at l relatively short intervals so as to maintain a constant supply of relatively high heated air.

A branch flue conduit 40 is connected with the waste gas main 18 and the flue 25 in the base 21 of the regenerator 17 to permit hot waste gasesto flow into the regenerator. A cooled waste gas conduit 41 is connected with the outlet of the flue 27 of the regenerator 17 and with the inlet port of an exhauster 42. The exhauster 42 has its outlet or discharge port connected to a conduit 43 leading into a cooled waste gas stack 44.

A blower 45 is provided for supplying air under pressure to theregenerator 17 and has its outlet port connected by a conduit 46 with the cold air supply conduit 29 of the regenerator and by a branch conduit 47 with the air supply main 16. The conduit 46 is provided with a valve 46fL by which the air supply to the regenerator may be shut off.

The branch conduit 47 is normally closed by a damper 48 and is only opened when it is desired to use cold instead of preheated air for combustion.

The hot air main 16 is connected with the hot air flue 31 of the regenerator by a i'lue 49 having a damper valve 49 therein.

The exhauster 42 and blower 45 are coupled together by a coupling shaft 50 and are operated by a single motor 5l.

The main vwaste gas flue 18 is provided with a damper 52 at a point between the point of connection of the branch ilue 40 and the stack 19, and this damper is operated by a standard pressure operating control 53 operable by the pressure within the waste gas manifold 13.

The damper 52 will operate to maintain a constant pressure in the manifold 13.

A bleeder conduit 55 connects at one end with the conduit 43 and at its other end with the hot waste gas branch ue 40 so as to permit the bleeding of cooled waste gases into the hot waste gases entering the regenerator to temper the hot gases, when desired.

The flow of cooled waste gases through the bleeder conduit 55 is automatically controlled by a damper 56 operated by a thermostat or other heat responsive device 57 mounted on the regenerator 17. The heat responsive device 57 is adapted to open the damper 56 when the regenerator becomes too hot and to close the damper when said regenerator cools.

A damper 58 is mounted in the cold air supply conduit 46 and a second damper 59 is mounted in the cooled waste gas conduit 41. The damper 58 is adapted to be moved toward closed position whenthe pressure builds up in the air manifold 8 due to any cause such .as shutting down of or reducing theair supply to one or more of the pits 2, and at the same time the damper 59 is adapted to be move'd toward closed position so as to decrease the induced flow of waste gases through the regenerator, since a lesser amount of air is entering said regenerator and therefore a lesser amount of heat exchange takes place. In order to automatically control the dampers 58 and 59 they are connected to a standard pressure controlr` mechanism, indicated at 60, which is operated by the pressure in the air manofold 8. The pressure in the air manifold 8 varies in direct proportion to the amount of heated air used by the pits, therefore the pressure control apparatus will operate the dampers in accordance with the amount of heated air used.

A cooled waste gas manifold 78 is mounted parallel with and above the air manifold 8' and connected with the lower end of the cooled waste gas stack 44 by a conduit 79. Branch conduits 80 lead from the waste gas manifold '78 to each of the fuel and air mixing chambers 5. A valve or damper 81 is mounted in the stack 44 above the point of communication of the conduit 79 and is adapted to be automatically regulated by a pressure regulator 82 which is connected by a pressure line 82a with the manifold 78 so as to maintain a constant pressure of cooled Waste gases in the lower portion of the stack 44, conduit 79 and manifold 78.

A manually operated valve 85 is provided in each of the branch conduits 80 by which the ow of waste gases to each of the mixing chambers may be controlled.

While I have shown the manifold being connected by the conduit '79 to the stack 44, it will be understood that the conduit 79 may be connected to any other source of the waste gases under pressure. In some cases it may be desired to discharge the cooled waste gases into the main stack 19, and in this case the valve or damper 81 would be mounted in the conduit 79 which would be connected to the stack 19 at a point beyond the damper 52.

It will also be understood that, if desired, automaticvalves operable by temperature responsive means in the pits may be substituted for the valves 85.

In carrying out the method of this invention the gas and air pressures and volumes are regulated to provide a maximum of ame volume'and temperature so as to carry the ame throughout the pit and heat the ingots or other material in the shortest time. As the upper portions of the ingots are heated to a predetermined temperature, which is that approaching a molten state, the ame temperature of the pit is reduced Without reducing the fiame volume by opening the valve 85, and permitting cooled waste gases to flow into the combustible mixture in the mixing chamber 5, thus diluting the mixture and lowering the B. t. u. value thereof. The valve will be regulated so as to reduce the flame temperature to approximately the temperature at which it is desired to heat the ingots, and the heating will thus proceed without interruption.

It will belnoted that the pressure regulator 82 receives its pressure from the manifold 78 so that regardless of the number of pits using the cooled waste gases, the pressure in the manifold will be maintained..

The waste gases are under pressure from the exhauster 42 which pulls them through the regenerator 17, and said gases are at substantially the same temperature of the preheated air so that the temperature of the combustible mixture is maintained'.

The invention has been illustrated in connection with a regenerator inwhich the waste gases are rst passed through the regenerative chamber and then cut off while the air is passed through the same.l

There are certain types of preheaters, generally called recuperators, where tiles are used with separate passages for the air and for the waste gases and where there is liability of leakage be-\ tween the two passages so that theair cannot economically be carried at a higher pressure than the gases. There are other styles of recuperators in which there is no liability of leakage and where pressure may be used on the air. The present invention, therefore, is not restricted to regenerators in the specific sense of the word but it is applicable to all styles of preheaters which are adapted to the supplying of air under pressure.

While I have described a method composed of a certain sequence of novel steps and a certain specific embodiment of apparatus for carrying out said. method, it will be understood that I do not wish to be limited thereto since various modifications may be made in both the method and apparatus without departing from the scope of my invention, as defined in the appended claims.

1. The method of operating an ingot pit furnace having a preheater for heating the air supplied to support combustion and wherein the flame impinges on the material which consists in providing a mixture of fuel and rair adapted to provide a predetermined flame temperature to heat the ingots in said pit, passing the hot waste gases through said preheater to preheat the air to be mixed with the fuel, maintaining said ame temperature until the portions of said ingots in contact with the flame entering said pit reach a predetermined temperature, then leaning down the flame temperature while maintaining, the ame by by-passing controlled amounts of the cooled waste gases after they have passed through said preheater under pressure into said mixture of fuel and air so as to prevent burning and excessive scaling of the ingots.

2. The method of operating an ingot pit furnace having a preheaterfor heating the air supplied to support combustion and wherein the flame impinges on the material which consists in providing a mixture of fuel and air adapted to provide a predetermined flame temperature to heat the ingots in -said pit, passing the hot waste gases through the preheater to preheat the air to be mixed with the fuel, maintaining said flame temperature until the portions of said ingots in contact with the flame entering said pit reach a predetermined temperature, then leaning down the flame temperature while maintaining the flame by by-passing controlled amounts of waste gases from said pit back into the mixture of fuel and air under pressure so as to prevent burning and excessive scaling of the ingots.

v3. The method of operating a preheating furnace of the direct heating type, which comprises mixing fuel and air thereinin quantities suflicient to provide a predetermined flame temperature, directing the flame so as to impinge on the material, removing the waste gases from the furnace pit, cooling at least a portion of the waste gases, and supplying controlled amounts of the cooled waste gases to said mixture of fuel and air to lean down the fuel mixture whereby a lower flame temperature in the furnace is obtained.

4. The method of operating a preheating furnace of the direct heating type, which comprises providing a mixture of fuel and air adapted to give a predetermined ame temperature, directing the flame to impinge on the material, conducting the waste gases from the heating chamber and cooling at least a portion thereof, maintaining the predetermined flame temperature until the portions of the material being treated in closest proximity to the flame attain a predetermined temperature, then reducing the flame temperature by conducting cooled waste gases M0 waste gases under pressure after they have passed through said preheater into said mixture of fuel and air to lean down the fuel mixture and remeans gases from each of said chambers, cooling at least a portion ot said waste gases, and supplying controlled amounts of the cooled waste gasesv under constant pressure from a single main to said mixture of fuel and air in each of said chambers to lean down the fuel mixture, whereby a lower ame temperature is obtained in each of said chambers.

ALBERT L. CULBERTSON.

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